1. Field of the Invention
The present invention relates to a method of repairing or reinforcing worn-out underground buried drainpipes through a trenchless rejuvenation technology and, more particularly, to a method of repairing or reinforcing such worn-out underground buried drainpipes by RTM (resin transfer molding) process using both flexible tubes and bagging films, the method being carried out by primarily inserting a reinforcement into a desired position within a target worn-out underground buried drainpipe, the reinforcement consisting of a fiber preform internally having a flexible tube axially extending along the central axis of the preform and externally wrapped with an adhesive-coated flexible bagging film to be protected from sewage or underground water left within the drainpipe, and transferring thermosetting resin to the fiber preform through the flexible tube to impregnate the preform with the resin, and finally curing the impregnated resin in the fiber preform, thus simply and easily repairing or reinforcing such worn-out underground buried drainpipes while reducing the repairing or reinforcing cost in comparison with conventional excavation and trenchless rejuvenation technologies.
2. Description of the Prior Art
As well known to those skilled in the art, at least 40xcx9c50% of pipes of drainage systems laid underground have been reduced in their strength, and partially cracked, broken and corroded before a lapse of their expected life span due to careless management, and so they undesirably allow a leakage of sewage into soil to finally contaminate soil and underground water in addition to causing a ground subsidence.
The cracked or broken drainpipes also allow rainwater and underground water to flow into drainpipes through cracks, thereby undesirably increasing the sewage disposal cost. Another problem experienced in the conventional drainage systems is that they force users to pay excessive money and waste excessive labor and time while managing, repairing or replacing the underground buried drainpipes. That is, when it is desired to manage, repair or replace drainpipes laid underground since the pipes are reduced in their strength, partially cracked, broken or corroded before a lapse of their expected life span, it is necessary to excavate earth around target pipes, thus increasing the cost and being very inconvenient to workers while managing, repairing or replacing the pipes.
In many nations, most pipes for drainage systems had been somewhat roughly designed, manufactured and buried underground without carefully considering the dynamic relation between the expected life span of the pipes, the depth of the pipes under the ground surface, and surface load applied to the pipes laid underground. Due to the above-mentioned problem experienced in the design, manufacture and laying of the drainpipes in addition to careless management of the pipes after laying the pipes underground, most drainpipes are regrettably worn-out, reduced in their strength, partially cracked, broken and corroded before a lapse of their expected life span. Such cracked or broken drainpipes undesirably allow a leakage of sewage into soil to finally contaminate soil and underground water in addition to causing a ground subsidence, and also allow underground water and rainwater to flow into the drainpipes, thereby increasing the quantity of sewage and increasing the sewage disposal cost.
When drainpipes are worn-out, reduced in their strength, partially cracked, broken and corroded as described above, earth has to be excavated in a large area around the target pipes using power excavators to allow replacement of the existing pipes with new pipes, while closing a road and regulating the traffic for a lengthy period of time. Furthermore, such a conventional method undesirably results in a breakage of pavements before a lapse of expected life span of the pavements, social and financial burden on the community due to the closing of the road and the regulating of the traffic for a lengthy period of time, and consumption of excessive labor and time for management of drainpipes.
In an effort to overcome such problems experienced due to the excavation of earth while managing or repairing drainage systems, a variety of trenchless rejuvenation technologies have been proposed and preferably used. Such trenchless rejuvenation technologies are particularly advantageous in that it is possible to remarkably save time, labor and money while managing or repairing the drainpipes buried underground. The trenchless rejuvenation technologies are also preferably usable for the management or repair of the pipes of waterworks in addition to the pipes of drainage systems.
Well-known trenchless rejuvenation technologies for underground buried pipes are classified into several types: reverse lining processes, slip lining processes, cured-in-place lining processes (CIPL), close-fit lining processes, spirally wound pipes lining processes and etc. Of such well-known trenchless rejuvenation technologies, a reverse lining process using unwoven fabric tubes impregnated with proper resin, such as polyester, and a spirally wound pipes lining process using thermoplastic resin have been most preferably and widely used.
In the conventional reverse lining process, it is necessary to keep the unwoven fabric tubes impregnated with polyester within a refrigerated container so as to prevent the polyester of the tubes from being cured before a practical use of the tubes at a construction field. Therefore, this process is problematic in that it is necessary to always use refrigerated transport vehicles for the unwoven fabric tubes impregnated with polyester and to use the tubes within a short period of time after the resin impregnation, thus being very inconvenient to workers and increasing the cost of repairing or reinforcing the drainpipes.
On the other hand, the conventional spirally wound pipes lining process using thermoplastic resin is problematic in that it is necessary to use large-sized heaters for melting the thermoplastic resin and additional power devices for forcibly transferring the highly viscous molten resin to a desired position within drainpipes laid underground.
In addition, a resin transfer molding process (RTM) for repairing or reinforcing the pipes without excavating earth has been proposed and used. However, the conventional RTM process is problematic in that underground water or sewage left within existing pipes is naturally and undesirably impregnated into fabric preforms, thus reducing the resin impregnation capability of the preforms and deteriorating the processing effect, and failing to accomplish a desired strength of the repaired or reinforced pipes.
Since the conventional spirally wound pipes lining processes use thermoplastic resin, it is necessary to inject an adhesive agent under pressure into the gap between a target drainpipe and an extruded resin tube or to forcibly expand the extruded resin tube so as to bring the resin tube into close contact with the internal surface of the target drainpipe. However, it is very difficult to perform such a process of bringing the resin tube into close contact with the drainpipe, and so the conventional spirally wound pipes lining processes fail to accomplish desired processing effect or desired strength of repaired or reinforced pipes.
Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and an object of the present invention is to provide a method of repairing or reinforcing worn-out drainpipes by a resin transfer molding process using both flexible tubes and bagging films, which uses thermosetting resin capable of improving the adhesiveness between reinforcements and worn-out drainpipes without any separate adhesive agent, and which is thus free from any separate process of forcing the resin tubes to come into close contact with the drainpipes, different from the conventional spirally wound pipes lining process and thereby saving time while repairing or reinforcing the worn-out drainpipes, and which does not require any consideration of prevention of resin curing during the process, different from the conventional reverse lining process, thus being free from use of refrigerated transport vehicles and being very convenient to workers, and reducing the cost of repairing or reinforcing the worn-out drainpipes.
In order to accomplish the above object, the present invention provides a method of repairing or reinforcing such worn-out drainpipes by a resin transfer molding process using both flexible tubes and bagging films, which comprises the steps of: inserting a reinforcement into a desired position within a target worn-out drainpipe buried underground, the reinforcement consisting of a fiber preform internally having a flexible tube, such as a silicon tube, axially extending along the central axis of the preform and wrapped with an adhesive-coated flexible film as a bagging film to provide protection from sewage or underground water; expanding the flexible tube to bring the fiber preform into close contact with the interior surface of the target drainpipe; sealing opposite ends of the reinforcement with lids; and transferring thermosetting resin into the fiber preform to impregnate the preform with the thermosetting resin, and finally curing the impregnated resin in the fiber preform.